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  • C07C2/864—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon the non-hydrocarbon contains only oxygen as hetero-atoms the non-hydrocarbon is an alcohol
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  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
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  • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
  • B01J29/42—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing iron group metals, noble metals or copper
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  • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
  • B01J2229/10—After treatment, characterised by the effect to be obtained
  • B01J2229/12—After treatment, characterised by the effect to be obtained to alter the outside of the crystallites, e.g. selectivation
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  • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
  • B01J2229/30—After treatment, characterised by the means used
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  • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
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  • C07C2521/00—Catalysts comprising the elements, oxides or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium or hafnium
  • C07C2521/10—Magnesium; Oxides or hydroxides thereof
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  • C07C2523/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of noble metals
  • C07C2523/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of noble metals of the platinum group metals
  • C07C2523/42—Platinum
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  • C07C2523/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of noble metals
  • C07C2523/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of noble metals of the platinum group metals
  • C07C2523/46—Ruthenium, rhodium, osmium or iridium
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  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2527/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
  • C07C2527/14—Phosphorus; Compounds thereof
• • C—CHEMISTRY; METALLURGY
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  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2529/00—Catalysts comprising molecular sieves
  • C07C2529/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites, pillared clays
  • C07C2529/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • C07C2529/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals
  • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S585/00—Chemistry of hydrocarbon compounds
  • Y10S585/8995—Catalyst and recycle considerations
  • Y10S585/906—Catalyst preservation or manufacture, e.g. activation before use

Definitions

• the present invention relates to a process for the selective alkylation of toluene, benzene, naphthalene, alkyl naphthalene and mixtures thereof with an oxygen-containing alkylation agent.
• the process uses a catalyst comprising a selectivated molecular sieve which has been modified by the addition of at least one hydrogenation component, wherein at least one of the following conditions is met: (a) the selectivated molecular sieve has an alpha value of less than 100 prior to the incorporation the hydrogenation component, or (b) the selectivated and hydrogenated molecular sieve used in the selective alkylation process has an alpha value of less than 100.
• the process of this invention provides high selectivity for the alkylated product while reducing catalyst deactivation.
• the para-xylene isomer is of particular value as a large volume chemical intermediate.
• One method for manufacturing para-xylene is by disproportionation of toluene into xylenes.
• a disadvantage of this process is that large quantities of benzene are also produced.
• Another process for manufacturing para-xylene is the isomerization of a feedstream that contains non-equilibrium quantities of mixed ortho- and meta-xylene isomers and is lean with respect to para-xylene content.
• a disadvantage of this process is that the separation of the para-xylene from the other isomers is expensive.
• Patent Number 4,670,616 involves the production of xylenes by the methylation of toluene with methanol using a borosilicate zeolite catalyst which is bound by a binder such as alumina, silica, or alumina-silica.
• a disadvantage of known toluene methylation catalysts is that methanol selectivity to para-xylene, the desirable product, has been low, in the range of 50-60%. The balance is wasted on the production of coke and other undesirable products.
• Attempts to increase the para-xylene selectivity have been conducted, however, it has been found that as para-xylene selectivity increases, the lifespan of the catalyst decreases. It is believed that the rapid catalyst deactivation is due to build up of coke and heavy by-products on the catalyst.
• the limited catalyst lifespan typically necessitates the use of a fmidized bed reactor wherein the catalyst is continuously regenerated. However, such a system usually requires high capital investment.
• a preferred system for toluene methylation is to use a fixed bed reactor because of lower capital investment.
• a suitable catalyst is found that provides a sufficient lifespan, with a sufficient selectivity to the desired product, fixed bed systems are simply impractical.
• the present invention satisfies this need.
• the invention is a process for forming a selectively alkylated aromatic compound comprising reacting an alkylating agent with a feed comprising an aromatic compound selected from the group consisting of toluene, benzene, naphthalene, alkyl (naphthalene and mixtures thereof in the presence of a catalyst under alkylation reaction conditions, said catalyst comprising a selectivated molecular sieve and at least one hydrogenation metal, wherein at least one of the following conditions is satisfied: (a) the selectivated molecular sieve has an alpha value of less than 100 prior to incorporation of said at least one hydrogenation metal, or (b) the selectivated and hydrogenated molecular sieve has an alpha value of less than 100.
• Figures 1 - 12 and 14 - 18 are plots showing the para-selectivity of various catalysts in a toluene methylation process.
• Figure 13 is a graph showing the effect of hydrogenation metals, water and phosphorus on reducing methanol decomposition in a toluene methylation process.
• the present invention relates to a process for the selective alkylation of toluene, benzene, naphthalene, alkyl naphthalene and mixtures thereof with an oxygen-containing alkylation agent.
• the process uses a catalyst comprising a selectivated molecular sieve, preferably a para-selective molecular sieve, that has. been modified by the addition of at least one hydrogenation component.
• a selectivated molecular sieve has an alpha value of less than 100 prior to the incorporation of the hydrogenation component
• the selectivated and hydrogenated molecular sieve has an alpha value of less than 100.
• the catalyst when used in this process, has an extended catalyst lifetime, while providing para-selectivity of greater than 60%, more preferably greater than 75%, more preferably greater than 80%, even more preferably greater than 85% and most preferably greater than 90%.
• the process is a toluene or benzene methylation process, which forms para-xylene at these preferred para-selectivity ranges.
• Catalysts suitable for use in the present invention include any catalyst that is effective for the alkylation of toluene, benzene, naphthalene, alkyl naphthalene or mixtures thereof. Preferably, the catalyst will be effective for the preferred process of toluene or benzene methylation.
• Catalysts used in the present invention include naturally occurring and synthetic crystalline molecular sieves. Examples of such molecular sieves include large pore molecular sieves, intermediate size pore molecular sieves, and small pore molecular sieves. These molecular sieves are described in "Atlas of Zeolite Framework Types", eds. Ch.
• a large pore molecular sieve generally has a pore size of at least about 7 A and includes IWW, LTL, VFI, MAZ, MEI, FAU, EMT, OFF, *BEA, and MOR structure type molecular sieves (IUPAC Commission of Zeolite Nomenclature).
• Examples of large pore molecular sieves include ITQ-22, mazzite, offretite, zeolite L, NPI-5, zeolite Y, zeolite X, omega, Beta, ZSM-3, ZSM-4, ZSM-18, ZSM-20, SAPO-37, and MCM-22.
• An intermediate pore size molecular sieve generally has a pore size from about 5A to about 7A and includes, for example, ITH, ITW, MFI, MEL, MTW, EUO, MTT, HEU, FER, MFS, and TON structure type molecular sieves (IUPAC Commission af Zeolite Nomenclature).
• intermediate pore size molecular sieves examples include ITQ-12, ITQ-13, ZSM-5, ZSM-12, ZSM-22, ZSM-23, ZSM-34, ZSM-35, ZSM-38, ZSM-48, ZSM-50, ZSM-57, silicalite, and silicalite 2.
• a small pore size molecular sieve has a pore size from about 3A to about 5A and includes, for sxample, CHA, ERI, KFI, LEV, and LTA structure type molecular sieves (IUPAC Commission of Zeolite Nomenclature).
• small pore molecular sieves examples include ZK-4, SAPO-34, SAPO-35, ZK-14, SAPO-42, ZK-21, ZK-22, ZK-5, ZK- 20, zeolite A, erionite, chabazite, zeolite T, gmelinite, and clinoptilolite.
• the intermediate pore size molecular sieve will generally be a composition having the following molar relationship: X 2 O 3 :(n) YO 2 wherein X is a trivalent element such as aluminum, iron, boron, and/or gallium and Y is a tetravalent element such as silicon, tin, and/or germanium; and n has a value greater than 12, said value being dependent upon the particular type of molecular sieve and the desired alpha value of the molecular sieve, in accordance with this invention.
• n is preferably greater than 10 and preferably, from 20:1 to 200:1.
• the molecular sieve catalyst is selectivated for the production of the desired alkylated product, which in the preferred embodiment is para-xylene.
• the catalyst can be selectivated by treating its surface with compounds of phosphorus and/or magnesium and/or various metal oxides such as alkaline earth metal oxides, e.g., calcium oxide, magnesium oxide, etc. rare earth metal oxides, lanthanum oxide, and other metal oxides such as boron oxide, titania, antimony oxide, and manganese oxide.
• Preferred ranges for such treatment are from about 0.1 wt.% to 25 wt.%, more preferably from about 1 wt.% to about 10 wt.% of such compounds based on the weight of the catalyst.
• the selectivation may also be accomplished by depositing coke on the catalyst.
• Coke selectivation can be carried out during the methylation reaction, such as by running the methylation reaction at conditions which allow the deposition of coke on the catalyst.
• the catalyst can be preselectivated with coke, for example, by exposing the catalyst in the reactor to a thermally decomposable organic compound, e.g., benzene, toluene, etc. at a temperature in excess of the decomposition temperature of said compound, e.g., from about 400°C to about 650°C, more preferably 425°C to about 550°C, at a WHSN in the range of from about 0.1 to about 20 lbs.
• a thermally decomposable organic compound e.g., benzene, toluene, etc.
• a silicon compound may also be used to selectivate the catalyst.
• the silicon compound may comprise a polysiloxane including silicones, a siloxane, and a silane including disilanes and alkoxysilanes. As is known to those of ordinary skill in the art, multiple treatments may be employed to effect various degrees of selectivation.
• Silicones that can be used to selectivate the catalyst include the following:
• R ⁇ is hydrogen, fluoride, hydroxy, alkyl, aralkyl, alkaryl or fluoro-alkyl.
• the hydrocarbon substituents generally contain from 1 to about 10 carbon atoms and preferably are methyl or ethyl groups.
• R 2 is selected from the same group as Ri, and n is an integer of at least 2 and generally in the range of 2 to about 1000.
• the molecular weight of the silicone employed is generally between about 80 to about 20,000 and preferably about 150 to about 10,000.
• Representative silicones include dimethylsilicone, diethylsilicone, phenylmethylsilicone, methyl hydrogensilicone, ethylhydrogensilicone, phenylhydrogensilicone, fluoropropylsilicone, ethyltrifluoroprophysilicone, tetrachlorophenyl methyl methylethylsilicone, phenylethylsilicone, diphenylsilicone, methyltrisilicone, tetrachlorophenylethyl silicone, methylvinylsilicone and ethylvinylsilicone.
• the silicone need not be linear but may be cyclic as for example hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, hexaphenyl cyclotrisiloxane and octaphenylcyclotetrasiloxane. Mixtures of these compounds may also be used as well as silicones with other functional groups.
• Useful siloxanes and polysiloxanes include as non-limiting example hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethyl cyclopentasiloxane, hexamethyldisiloxane, octamethytrisiloxane, decamethyltetrasiloxane, hexaethylcyclotrisiloxane, octaethylcyclo tetrasiloxane, hexaphenylcyclotrisiloxane and octaphenylcyclo-tetrasiloxane.
• Useful silanes, disilanes, or alkoxysilanes include organic substituted silanes having the general formula:
• R is a reactive group such as hydrogen, alkoxy, halogen, carboxy, amino, acetamide, trialkylsilyoxy
• R l5 R 2 and R 3 can be the same as R or can be an organic radical which may include alkyl of from 1 to about 40 carbon atoms, alkyl or aryl carboxylic acid wherein the organic portion of alkyl contains 1 to about 30 carbon atoms and the aryl group, contains about 6 to about 24 carbons which may be further substituted, alkylaryl and arylalkyl groups containing about 7 to about 30 carbon atoms.
• the alkyl group for an alkyl silane is between about 1 and about 4 carbon atoms in chain length. Mixtures may also be used.
• the silanes or disilanes include, as non-limiting examples, dimethylphenylsilane, phenytrimethylsilane, triethylsilane and hexamethyldislane.
• Useful alkoxysilanes are those with at least one silicon-hydrogen bond.
• the molecular sieve catalyst is selectivated using the combined selectivation techniques of contacting the molecular sieve with a silicon compound and treatment with magnesium and/or phosphorus.
• the molecular sieve will be incorporated with binder material resistant to the temperature and other conditions employed in the process.
• suitable binder material include clays, alumina, silica, silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia, and silica-titania, as well as ternary compositions, such as silica-alumina-thoria, silica-alumina- zirconia, silica-alumina-magnesia and silica-magnesia-zirconia.
• the molecular sieve may also be composited with zeolitic material such as the zeolitic materials that are disclosed in U. S. Patent 5,993,642.
• the relative proportions of molecular sieve and binder material will vary widely with the molecular sieve content ranging from between about 1 to about 99 percent by weight, more preferably in the range of about 10 to about 70 percent by weight of molecular sieve, and still more preferably from about 20 to about 50 percent.
• Catalysts particularly suited for the methylation reaction are zeolite bound zeolite catalysts. These catalysts, as well as their method of preparation, are described in U. S. Patent 5,994,603, which is hereby incorporated by reference.
• the zeolite bound zeolite catalysts will comprise first crystals of an acidic intermediate pore size first molecular sieve and a binder comprising second crystals of a second molecular sieve.
• the zeolite bound zeolite catalyst contains less than 10 percent by weight based on the total weight of the first and second zeolite of non-zeolitic binder, e.g., amorphous binder.
• An example of such a catalyst comprises first crystals of a MFI or MEL structure type, e.g., ZSM-5 or ZSM-11, and a binder comprising second crystals of MFI or MEL structure type, e.g., Silicalite 1 or Silicalite 2.
• Hydrogenation metals useful in accordance with this invention encompass such metal or metals in the elemental state (i.e. zero valent) or in some other catalytically active form such as an oxide, sulfide, halide, carboxylate and the like.
• the metal is used in its elemental state.
• suitable hydrogenation metals include Group NIIIA metals (i.e., Pt, Pd, Ir, Rh, Os, Ru, ⁇ i, Co and Fe), Group IVB metals (i.e., Sn and Pb), Group VB metals (i.e., Sb and Bi), and Group VILA metals (i.e., Mn, Tc and Re).
• the hydrogenation component may also be accompanied by another metal promoter.
• the amount of Group NIIIA hydrogenation metal present on the catalyst will usually be from about 0.1 wt.% to about 5 wt.% of hydrogenation metal based on the weight of the catalyst.
• the incorporation of the hydrogenation metal can be accomplished with various techniques known to those skilled in the art. For example, the metal can be incorporated into the catalyst by impregnation, or by ion exchange of an aqueous solution containing the appropriate salt, or by a combination of these methods.
• platinum in an ion exchange process, platinum can be introduced by using cationic platinum complexes such as tetraammine-platinum (II) nitrate.
• the hydrogenation function can be present by physical intimate admixing, that is, the hydrogenation function can be physically mixed or extruded with the active catalyst. Physical intimate admixing can also be conducted by incorporating the hydrogenation function on a particle separate from the active catalyst, and then the particle carrying the hydrogenation function placed in close proximity to the catalyst.
• the hydrogenation metal can be impregnated onto an amorphous support that is co-mingled with the active molecular sieve catalyst such as described in U.S. Patent No. Re. 31,919 to Butter et al., incorporated by reference herein.
• Typical alkylating agents include methanol, ' dimethylether, methylchloride, methylbromide, methylcarbonate, acetaldehyde, dimethoxyethane, acetone, and dimethylsulfide.
• the preferred methylating agents are methanol and dimethylether.
• the methylating agent can also be formed from synthesis gas, e.g., the agent can be formed from the H 2 , CO, and/or CO 2 of synthesis gas.
• the methylating agent can be formed from the synthesis gas within the methylation reaction zone.
• methylating agents may be employed to methylate the benzene and/or toluene based on the description provided therein.
• either (a) the selectivated molecular sieve or (b) the selectivated and hydrogenated molecular sieve used in the alkyating process will have an alpha value of less than 100, more preferably less than 50, even more preferably less than 25, and most preferably less than 10.
• the alpha value is a measurement of the Bronsted acid activity of the selectivated molecular sieve, i.e. it discounts the effects of the addition of the hydrogenation component on the alpha value of the molecular sieve.
• the alpha test is described in U.S. Patent No. 3,354,078 and in the Journal of Catalysis, Vol. 4, 522-529 (1965); Vol. 6, 278 (1966); and Vol.
• the experimental conditions of the alpha test preferably include a constant temperature of 538°C. and a variable flow rate as described in detail in the Journal of Catalysis, Vol. 61, 395 (1980).
• molecular sieves having a higher silica to alumina ratio will have a lower alpha value.
• the alpha activity of a catalyst can be reduced in accordance with techniques known to those of ordinary skill in the art. For example, the alpha activity of a catalyst may be reduced by (1) steaming the catalyst at appropriate conditions, or (2) ion exchanging the catalyst with cations such as alkali metal ions. [0025]
• the alkylation reaction can be carried out in vapor phase.
• Reaction conditions suitable for use in the present invention include temperatures from about 300° C to about 700° C and preferably about 400° C to about 700° C.
• the reaction is preferably carried out at a pressure from about 1 psig (108 kPa) to 1000 psig (6996 kPa), more preferably from about 1 psig (108 kPa) to 150 psig (1136 kPa), and even more preferably about 1 psig (108 kPa) to 50 psig (446 kPa).
• the reaction is preferably carried out at a weight hourly space velocity of between about 0.1 and about 200, more preferably between about 1 to about 20, and even more preferably between about 6 and 12, and preferably between about 1 and about 100 weight of charge per weight of catalyst per hour.
• the molar ratio of toluene and benzene to alkylating agent can vary and will usually be from about 0.1:1 to about 20:1. Preferred ratios for operation are in the range of 2:1 to about 4:1.
• the alkylating agent is usually supplied to the reaction zone through multiple feed points, e.g., 3-6 feed points. The process is preferably conducted in the presence of hydrogen at a partial pressure of at least 5 psi (34 kPa).
• the system also includes water added to the feed, such that the molar ratio of hydrogen and/or added water to the aromatic compound and alkylating agent in the feed is between about 0.01 to about 10.
• the molecular sieve used in accordance with this invention has a hydrogenation metal comprising rhodium.
• the use of rhodium as the hydrogenation component has been found to reduce the amount of synthesis gas formed due to the decomposition of the alkylating agent (i.e. methanol in the preferred embodiment).
• the molecular sieve used in accordance with this invention has a hydrogenation metal comprising platinum, and a selectivating compound comprising phosphorus.
• a hydrogenation metal comprising platinum
• a selectivating compound comprising phosphorus.
• ZSM-5/ SiO 2 , 1/16" cylindrical was loaded with 0.1 wt.% Pt by incipient wetness impregnation with tetraammine platinum nitrate, followed by drying at 250°F (121°C) and calcining for 1 hour in air at 660°F (349°C).
• the platinum-containing extrudate was then selectivated with silica by impregnating with 7.8 wt.% DowTM- 550 silicone in decane, stripping the decane, and calcining. This procedure was repeated three more times.
• the 4X selectivated material was then steamed in 100% steam at atmospheric pressure for 24 hours at 1000°F (538°C). The final material had an alpha value of 17.
• ZSM-5/ SiO 2 , 1/16" cylindrical was selectivated with silica by impregnating with 7.8 wt.% DowTM-550 silicone in decane, stripping the decane, and calcining at 1000°F. This procedure was repeated two more times. The 3X selectivated material was then steamed in 100% steam at atmospheric pressure for 24 hours at 1000°F (538°C). The final material had an alpha value of 15.
• Example 4 Steamed, 0.1% Pt impregnated, 3X Silica-Selectivated H-ZSM- 5/SiO 2 (Catalyst D)
• Example 3 The catalyst of Example 3 was loaded with 0.1 wt.% Pt by incipient wetness impregnation with tetraammine platinum nitrate, followed by drying at 250°F (121°C) and calcining for 3 hours in air at 660°F (349°C).
• ZSM-5/ SiO 2 , 1/16" cylindrical was loaded with 0.1 wt.% Pt by incipient wetness impregnation with tetraammine platinum nitrate, followed by drying at 250°F (121°C) and calcining for 3 hours in air at 660°F (349°C).
• the platinum- containing extrudate was then selectivated with silica by impregnating with 7.8 wt.% DowTM-550 silicone in decane, stripping the decane, and calcining at 1000°F (538°C). This procedure was repeated two more times.
• the 3X selectivated material was then steamed in 100% steam at atmospheric pressure for 18 hours at 1000°F (538°C). The final material had an alpha value of 14.
• Example 6 Catalytic Evaluations of Catalysts A and B
• the catalyst load was 2 g for the base catalyst runs. For the 1 :3 molar feed mixture, the maximum toluene conversion expected from reaction with methanol would be about 33%.
• Methanol utilization is reported as (moles of xylene formed - moles of benzene formed) / (moles of methanol converted). Benzene is subtracted to account for any xylene formed by the disproportionation of toluene to xylene plus benzene.
• Catalyst A is impregnated with a platinum hydrogenation component, however, the test data indicates poor stability at 10 hours.
• the data indicates that impregnation of a hydrogenation component can enhance the catalyst stability for a toluene methylation process, while maintaining high para-xylene selectivity, when the catalyst has a low alpha value.
• Figures 3-5 compare the performance of Catalysts C, D, and E.
• a 450:1 Si:Al 2 HSLS ZSM-5 molecular sieve is spray dried in a silica/alumina/clay/phosphorus matrix followed by calcination in air at 540°C.
• the base material is then steamed-selectivated at high temperatures (approximately 1060°C).
• the resulting material had an alpha value of 2.
• Example 8 The catalyst of Example 8 was loaded with 0.1 wt.% Pt by incipient wetness impregnation with tetraammine platinum nitrate, followed by drying at 250 °F (121°C) and calcining for 3 hours in air at 660 °F (349°C).
• the catalyst load was 2 g. For the 1 :2 molar feed mixture, the maximum toluene conversion expected from reaction with methanol would be about 50%.
• Methanol utilization is reported as (moles of xylene formed - moles of benzene formed) / (moles of methanol converted). Benzene is subtracted to account for any xylene formed by the disproportionation of toluene to xylene plus benzene.
• Catalyst H is a zeolite-bound-zeolite having a core zeolite crystal comprised of ZSM-5 (70-75:1 Si:Al 2 ) bound with silica (binder content 30% of final catalyst), where the silica binder is converted to silicalite (> 900:1 Si:Al 2 ).
• the preparation of such a zeolite-bound-zeolite is described in U.S. Patent Nos. 5,665,325 and 5,993,642.
• the final material had an alpha value of 630.
• Methanol utilization is reported as (moles of methanol converted) / (moles of xylene formed - moles of benzene formed). Benzene is subtracted to account for any xylene formed by the disproportionation of toluene to xylene plus benzene.
• Catalyst H shows good stability and methanol utilization, but no enhanced para- selectivity.
• the toluene conversion declines with the time on stream. This decline is mainly due to the loss of catalyst activity on the toluene disproportionation reaction.
• the benzene formation decreased from 7% to less than 2% within 24 hours.
• Example 12 7 wt.% Mg impregnated Catalyst H (Catalyst I) [0044] Catalyst H was selectivated with 7 wt.% of magnesium (Mg) in the following manner. Ammonium nitrate hexahydrate (55.4g) was dissolved in 27.95g deionized water. This solution was slowly added to lOOg of Catalyst H in a rotary impregnator. The catalyst was dried at ambient conditions overnight. The catalyst was calcined at 660°F (349°C) for 3 hours in full air (3 vol/vol/min). The resulting material had an alpha value of 20.
• Mg magnesium
• magnesium impregnation treatment boosts the para-xylene selectivity from about 30% to about 60%.
• a slight impact on the catalyst stability, toluene conversion and methanol utilization is shown.
• Figure 9 also shows that higher reaction pressures (150 psig (1136 kPa) versus 50 psig (446 kPa) result in lower para-xylene selectivity (58% versus 65%).
• Example 13 1.5wt.% P, 7 wt.% Mg impregnated Catalyst H (Catalyst J) [0046]
• the catalyst of Example 12 was modified with 1.5 wt.% phosphorus (P), and the resulting material had an alpha value of 37.
• Catalyst J was evaluated in a toluene methylation reaction at different hourly space velocities, with and without co-feeding water, and at different reaction temperatures. The data show that increasing the hourly space velocity from 4 to 8 resulted in higher para-xylene selectivity (78% versus 63%). In addition, the toluene conversion and methanol utilization were slightly improved.
• Example 14 2.5wt% P, 7wt% Mg impregnated Catalyst H (Catalyst K) [0047]
• the catalyst of Example 12 was modified with 2.5 wt.% phosphorus, which resulted in a final material with an alpha value of 37.
• increasing the phosphorus content over the 1.5 wt.% provided in Example 13 improves the para-xylene selectivity from 75% to 93% at the same conditions.
• the stability of the catalyst is affected, with the higher phosphorus content of this Example 14 deactivating the catalyst faster than the lower phosphorus content catalyst of Example 13.
• Example 15 0.1wt% Rh, 2.5wt%P, 7wt% Mg impregnated Catalyst H (Catalyst L)
• Example 14 The catalyst of Example 14 was modified with 0.1 wt% of rhodium
• Rhodium chloride hydrate was dissolved in deionized water. This solution was slowly added to the catalyst of Example 14 in a rotary impregnator. The catalyst was mixed well and then dried at 250°F (121°C) overnight. The catalyst was then calcined in full air at 660°F (349°C) for 3 hours (3 vol/vol/min).
• gas phase analysis indicates that the use of rhodium as the hydrogenation component for a molecular sieve in accordance with this invention reduces the unwanted methanol decomposition to synthesis gas, in particular when water is co-fed into the reactor.
• MTPX refers to a 4X silica selectivated H-ZSM-5/SiO 2 molecular sieve.
• Figure 13 shows that selectivation of the molecular sieve with phosphorus while co-feeding water inhibits the unwanted methanol decomposition to synthesis gas when used with other hydrogenation components.
• a molecular sieve catalyst in accordance with the limitations of this invention having platinum as the hydrogenation component and phosphorus as the selectivating component has a reduced methanol decomposition to synthesis gas when water is co-feed into the reactor.
• ZSM-5/SiO 2 , 1/16" cylindrical was selectivated with silica by impregnating with 7.8 wt.% DowTM-550 silicone in decane, stripping the decane, and calcining at 1000°F (538°C). This procedure was repeated two more times. The 3X selectivated material was then steamed in 100% steam at atmospheric pressure for
• Ammonium phosphate (2.08 g) was dissolved in 13.46 g deionized water and slowly added to 37.22 g of the catalyst above. After mixing, the catalyst was dried at 250°F (121°C) for 2 hours. The catalyst was then calcined in full air at 660°F (349°C) for 3 hours (3 vol/vol/min).
• Rhodium chloride hydrate (0.076g) was dissolved in 9.49 g of deionized water and slowly added to 30 g of the catalyst above. The catalyst was mixed well and then dried at 250°F (121°C) for 4 hours. The catalyst was then calcined in full air at 660°F (349°C) for 3 hours (3 vol/vol/min).
• the resulting catalyst had a composition of 0.1 wt.% Rh, 0.76 wt.% i
• Figure 14 shows the catalyst tested at different pressures, with and without co-feeding water.
• the catalyst is stable and selective.
• Example 17 Steamed, 3X Silica-Selectivated H-ZSM-5/SiO 2 [0057] Silica-bound H-ZSM-5 (0.4 ⁇ m, 26:1 Si:Al 2 ) extrudate (65/35
• ZSM-5/SiO 2 , 1/16" cylindrical was selectivated with silica by impregnating with 7.8 wt.% DowTM-550 1 silicone in decane, stripping the decane, and calcining at 1000°F. This procedure was repeated two more times. The 3X selectivated material was then steamed in 100% steam at atmospheric pressure for 24 hours at 925°F (496°C), 975°F (524°C) and 1000°F (538°C) to form three catalysts having alpha values of 51, 32 and 15, respectively.
• Alumina extrudate (100% Al 2 O 3 , 1/16" cylindrical) was loaded with 0.1 wt.% Pt by incipient wetness impregnation with tetraammine platinum nitrate, followed by drying at 250°F (121°C) and calcining for 3 hours in air at 660°F (349°C).
• the catalyst load was a mixture of 0.4 - 0.8 g of 0.1% Pt /Al 2 O 3 of Example 18 and 2 g for the respective steamed catalyst of Example 17.
• Catalyst N has a catalyst load of 0.8g of the extrudate of Example
• Catalyst O has a catalyst load of 0.8g the extrudate of Example 18 and 2 g of the steamed catalyst of Example 17 having an alpha value of 32.
• Catalyst P has a catalyst load of 0.4g the extrudate of Example
• each of Catalyst N, O and P indicate good stability.
• Catalyst O appears to maintain the highest para-xylene selectivity of 85% with toluene conversion at 7%.
• Catalyst P exhibits the highest toluene conversion at 14% with good para-xylene selectivity of 73%.
• This Example indicates that the hydrogenation function does not have to be located directly on the molecular sieve to be effective in accordance with this invention, as long as the hydrogenation function is in proximity to the molecular sieve.
• the hydrogenation metal can be impregnated onto an amorphous support that is co-mingled with the active molecular sieve catalyst.
• Example 20 0.1 %Rh, 3X Silica-Selectivated, 1%P impregnated ZSM- 5/SiO 2 (Catalyst Q)
• the 3X selectivated material was then loaded with 0.1 wt.% Rh by incipient wetness impregnation with rhodium chloride hydrate, drying at 250°F (121°C), and calcining for 3 hours in air at 660°F (349°C).
• the resulting catalyst had a composition of 0.1 wt.% Rh and 1 wt.% P and an alpha value of 1, prior to incorporation of the hydrogenation component.
• catalytic data shows that Catalyst Q maintains high para-selectivity and excellent catalyst stability.

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